A drug composition for inhibiting or preventing the metastasis of malignant tumors which includes at least one vasoprotector selected from among (i)-(iv), below, or a pharmacologically-acceptable salt thereof as an active ingredient. (i) Angiotensin II receptor antagonists (ii) HMG-CoA reductase inhibitors (iii) Ghrelin and derivatives thereof (iv) Adrenomedullin and derivatives thereof